Bipolar power semiconductor components, like power diodes, power IGBTs (insulated gate bipolar transistors), or power thyristors, include a first emitter region of a first conductivity type, a second emitter region of a second conductivity type, and a base or drift region arranged between the first and second emitter regions. The base region is of one of the first and second conductivity types and has a lower doping concentration than the first and second emitter regions. When the component is in its conducting or on-state, charge carriers of the first conductivity type are injected into the base region from the first emitter region, and charge carriers of the second conductivity type are injected into the base region from the second emitter region. These charge carriers form a charge carrier plasma in the base region. This plasma with charge carriers of the first and second conductivity type results in a low resistance of the component in the on-state.
When the component is switched off, i.e. when the component transits from its on-state into its off or non-conducting state these charge carriers that form the charge carrier plasma have to be removed from the base region. In this case, charge carriers of the first conductivity type flow in the direction of the first emitter region, and charge carriers of the second conductivity type flow in the direction of the second emitter region. When the component switches into its off-state, a space charge region starts to propagate in the base region. The generation of this space charge region together with the mobile charges that are extracted out of the plasma region may result in locally increased electric field strength. Dynamic avalanche occurs when the field strength reaches a critical value (ECRIT). Due to this avalanche generation and a positive feedback for carrier generation the current flow may become inhomogeneous.
This current crowding results in a high current density in regions where the electric field strength is locally increased. Since the formation of current filaments usually occurs in a relatively small area, the current flow is also limited to this small area. A high current flow in a small area of the base region may result in a strong heating of those regions in which the breakdown occurs. This may result in a damage or a degradation of the semiconductor component.
There is, therefore, a need to provide a semiconductor component which has an improved dynamic behavior, i.e. an improved behavior when switching from the on-state to the off-state.